Loss of vacuum when left foot braking
05-31-2019, 01:19 PM
#1
Le Mans Master
Thread Starter
Loss of vacuum when left foot braking
Has anyone experienced this on a road course?
Thanks,
Jim
Thanks,
Jim
06-06-2019, 08:02 AM
#2
Race Director
Member Since: Jul 2007
Location: Texas Hill Country
Posts: 10,763
Received 2,379 Likes
on
1,238 Posts
how are you measuring vacuum? the boost gauge?
if youre pressing the gas and brake at the same time then torque management will intervene causing a potential perception of vacuum loss
if youre pressing the gas and brake at the same time then torque management will intervene causing a potential perception of vacuum loss
06-06-2019, 04:42 PM
#3
Le Mans Master
Thread Starter
01-23-2021, 02:44 PM
#5
Le Mans Master
Thread Starter
Works GREAT. No issues now!
Jim
Jim
05-19-2021, 10:35 PM
#6
Drifting
Can you post a pic of the install please? Operations, didn’t you do something similar? How did it work out and can you post a picture please? Thanks
05-20-2021, 10:06 AM
#7
Drifting
We did swap out the Vac pump for the a race pump, when we went out to test we were also testing out our 2650R, cam, ported heads etc at the same time, the change made 850/800rw, but on track we started blowing a ton of oil through the PCV, we tried various catch cans and re plumbing the lines, but it volume of oil under WOT was to great for any of our solutions to work. We ran compression checks and found no issues there. On the last track test I took Sergio from LG as a passenger to watch the gauges and his laptop with HP tuners. He saw my dash oil pressure dip really low, so we killed the engine and was towed in.
Pulled the engine, only then did we find a piston broken, that cylinder was also really worn. Likely the piston was damaged a while back when the Callaway SC cooling brick failed and flooded the right cylinders with water. Unknown to anyone because it ran fine before turning it off a week prior, upon trying to start the engine we must of cracked the piston due to being it was hydrolocked, all we know is it would not turn over.
Long story short, it took a 0.010 over bore to clean up the worn cylinder, we ordered new pistons from Racetec, going on six weeks now waiting on them, then sending them on to Swain Tech for coating.
So the Race vac pump test in inconclusive for now.
Pulled the engine, only then did we find a piston broken, that cylinder was also really worn. Likely the piston was damaged a while back when the Callaway SC cooling brick failed and flooded the right cylinders with water. Unknown to anyone because it ran fine before turning it off a week prior, upon trying to start the engine we must of cracked the piston due to being it was hydrolocked, all we know is it would not turn over.
Long story short, it took a 0.010 over bore to clean up the worn cylinder, we ordered new pistons from Racetec, going on six weeks now waiting on them, then sending them on to Swain Tech for coating.
So the Race vac pump test in inconclusive for now.
05-20-2021, 11:38 AM
#8
Le Mans Master
Quite a story! Even with a broken piston, worn cylinder a good compression. Oil must have sealed it up pretty good. That Callaway SC cooling brick turned into an expensive ordeal. Report back with updates.
05-20-2021, 11:43 AM
#9
Le Mans Master
05-20-2021, 12:17 PM
#10
Drifting
Some will post a few more reasons, bit in the end, done well it good for some time savings.
Most pros will recommend not to introduce left foot braking until you are already a prettying fast advanced driver.
The following users liked this post:
range96 (05-21-2021)
05-21-2021, 01:25 PM
#11
Le Mans Master
There are various reasons for left foot braking, most are to get the weight transferred to neutral or to the front while still on throttle to keep momentum up and to get the traction on the front so the car will turn in. Sometimes your just wanting to begin braking before the right foot is off the gas completely, but for most its about another tool to assist in car placement, and rotation while carrying speed
Some will post a few more reasons, bit in the end, done well it good for some time savings.
Most pros will recommend not to introduce left foot braking until you are already a prettying fast advanced driver.
Some will post a few more reasons, bit in the end, done well it good for some time savings.
Most pros will recommend not to introduce left foot braking until you are already a prettying fast advanced driver.
On the ZR1 there is a 'hanging throttle' (lag between you let off the throttle and the computer dials in 0 throttle). I assume it's strictly for emission reasons. At initial brake application I still feel the car pulling.
05-21-2021, 03:07 PM
#12
Le Mans Master
Thread Starter
05-21-2021, 05:16 PM
#13
Race Director
Member Since: Oct 2000
Location: Deal's Gap 2004 NCM Motorsports track supporter
Posts: 13,915
Received 1,103 Likes
on
717 Posts
There are various reasons for left foot braking, most are to get the weight transferred to neutral or to the front while still on throttle to keep momentum up and to get the traction on the front so the car will turn in. Sometimes your just wanting to begin braking before the right foot is off the gas completely, but for most its about another tool to assist in car placement, and rotation while carrying speed
Some will post a few more reasons, bit in the end, done well it good for some time savings.
Most pros will recommend not to introduce left foot braking until you are already a prettying fast advanced driver.
Some will post a few more reasons, bit in the end, done well it good for some time savings.
Most pros will recommend not to introduce left foot braking until you are already a prettying fast advanced driver.
Don't confuse clutch with brake pedal though. Right Jim? Painrace was in passenger seat when I had off track excursion to the right out of the NCM sink hole. 
I would recommend making sure you use the far right side of brake pedal in an automatic if you are practicing on the street to develop left foot brake sensitivity. 
05-24-2021, 11:01 AM
#14
Le Mans Master
Thread Starter
It was a fun ride! Thanks Southern Son!
Painrace
Painrace
08-06-2021, 03:44 PM
#15
Drifting
Can either of you post a picture of your surge tank install please? I’m considering this due to the inconsistency of my brakes at the track. Thanks
08-09-2021, 02:23 PM
#17
Drifting
08-09-2021, 03:29 PM
#18
Drifting
Hope this helps
08-10-2021, 08:46 AM
#19
Drifting
That does help, thank you.